SiC Zener diode and Voltage References for extended operation (>1000 hr.) at 500 degrees C: SMD Planetary Division, High-Temperature Subsystems and Components for Long-Duration (months) Surface Operations

SiC and GaN are the materials of choice for High temperature electronics because of their wide bandgap and high chemical stability at high temperature and also because these technologies have recently seen a considerable development leading to commercialization on the consumer market. Although they both have acceptable thermal conductivity, SiC is exceptional in that regard, which prevents the occurrence of hot spots in the device when used at high power and high current densities. Several teams have been developing electronics devices for Venus like conditions. Power conditioning for these devices will be needed both for protection and for accuracy. In modern electronics, power conditioning is done using complex integrated circuits. However, GaN or SiC technology are not at the stage where these types of ICs are easily manufactured and tested within a reasonable amount of time. Therefore, discrete Zener diodes, which have been extensively used in earlier Si electronics (and are still used although less commonly) to stabilize voltages, shape signals and protect electronics from overvoltage events have a huge potential for SiC high temperature electronics. We propose the fabrication and investigation of high temperature (500°C) SiC Zener diodes using ion implantation and evaluate their long term degradation at high temperature. Two main configurations will be pursued: (i) a vertical device, for high power applications and (ii) a lateral device that can be integrated into SiC ICs that are being developed by other groups. The different elements necessary to make the high temperature device will come from expertise developed by the Auburn group in their ongoing and previous studies of devices such as 500°C MOSFET transistors and high temperature integrated circuits. A measurement setup was developed for our ongoing interest in high temperature electronics and will also be used in this case for study of the device behavior over time. The device will be stressed at high temperature (typically 500°C) for over 1000 hours and the characteristics of the device will be monitored during the test. Of interest are the capacity of the devices to regulate power with minimal drift over time. For such precision devices, contact degradation and the effect of passivation layers will have an important effect on the device performance. The effect of using ion-implanted doped layer as opposed to the conventional way of using epitaxially doped material will also be investigated. Our study therefore will give to other groups involved in the development of devices for NASA missions, the recipes to incorporate Zener diodes into their designs with established properties over time. The difficulties of the project reside in the presence of crystal defects in SiC such as basal plane and threading edge dislocations that are known to grow over time especially at high temperatures. Unfortunately these defects are more prominent in highly doped layers. They are known to reduce the performance of diodes and may result in faster degradation of the devices at high temperatures. The study proposes both the fabrication and the long-term study of the devices in a set up that allows the parallel biasing of several devices simultaneously at high temperature. Devices will be characterized in situ while at high temperature and be characterized after 1000 hours stress to observe the presence of dislocations and their extent.

This is a mature technology (TRL 7+) — the realistic path in is usually NASA's Technology Transfer Program: licensing an existing NASA patent, or a Space Act Agreement to use NASA facilities/expertise directly. NASA also runs a startup licensing program with no upfront fee for companies formed to commercialize a specific NASA technology.

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